| In order to analyze the influence of off line arc on the body potential of CRH3,taking CRH380BL as an example,the two aspects which include the conduction coupling and the radiation coupling are analyzed.We can establish the equivalent model of the transmission line about parameters of frequency of the off line arc from the perspective of the conduction coupling and simplify the model of arc transient equivalent to 3 lumped parameter circuits which have no direct connection topology by using the transmission line theory.According to Kirchhoff' law,we could calculate the results,and write programs to calculate the potential in MATLAB and analyze the relationship between arc and capacitance from the pantograph strip to the car's body,voltage phase and protection grounding.We can take the network as some electric basic oscillators and calculate the electric magnetic fields in round space by calculating he electric magnetic fields of electric basic oscillator.The relationship between electric magnetic fields and capacitance from the pantograph strip to the car's body,voltage phase and protection grounding can be analysised through comparing the result of calculation with measure.When the electromagnetic radiation of arc bounce to the car's body,the distributed voltage source will came into being on the car's body,but we can use the related theory of active transmission line model to calculate he body' s potential.The results show:1)The time of arc and the frequency of breakdown will decrease with the the increase of capacitance and body's potential.when the capacitor is more than 1000pF,the maximum value of potential approximately constant;The maximum value of potential is 920V for bow down which is associated with the phase voltage of traction;When the traction voltage phase is from 0° to 90°,arc time will decrease with the increase of phase;When the voltage phase is from 90° to 180°,arc time will increase with the increase of phase;Compared with the arc during bow down,both the body's potential and arc time less than drop arch;After installing protective grounding,the potential of the 2 car decreased from 780V to 4.8V and the potential of the 8 car decreased from 7.5V to 4V.2)If increasing the coupling capacitance between bow and body,high frequency electric field intensity is almost the same and the electric field intensity is 90dBuV/m if using the measuring method of 10 meters,but the low frequency increases gradually at the same time;After increasing protective grounding on the second body,the arc current increases 10A,but the radiation's value increase 2.3dBuV/m;When the voltage phase is from 0° to 180°,electric field radiation of high frequency increase with the increase of the phase.3)The induced current is the largest below the pantograph in the body.the farther away from the pantograph,the smaller the induction current;The induction voltage is only 3.8V on the body of 1 car,the induction potential is 95V on the body of the 2 car and the induction potential is 0.068V on the body of the 8 car.4)Because of the potential of speed sensor is not the same on the shielding layer,it will be into the core wire through capacitive coupling,which will make the speed sensor to be disturbed.The voltage increases with the increase of frequency,but when the frequency is more than 1MHz,the interference voltage will remain constant. |
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